Infinite scroll can have real performance problems and make for an irritating experience. http://www.fastcodesign.com/ is a site that (for me at least) is overly intrusive with its automatic loading it could use a pagination model to solve this.

Performance is the most common reason for this. Loading content upfront is very costly for very long lists. Modern interfaces usually load dynamically on scroll. However, this can be limited as well because you do not want to blow up your user's browser. Hence you should be conscious of the performance cost of enlarging a page with more content. That being said, most modern equipment can handle quite a bit of abuse.

Another reason for this could be to give the user landmarks in his navigation. A more common example are books. You use pages for references when looking up information for yourself, e.g. "this was a dozen of pages ago". Without a way to break the larger information space in navigable chunks, it would be highly improbable that you could effectively jump ahead or back, e.g. "this was 200-300 lines ago".